Several approaches for the study of hormonal control of metabolic progress in tissues of the developing fetus are proposed. We will study the control of heme formation by steroid hormones and metabolites in human fetal liver in mono-layer culture. This will include the control of DNA, RNA and protein synthesis in such cells. Another line of research is the control of surfactant synthesis in rabbit fetal lung. We are proposing to study the control of dipalmitoyl lecithin synthesis by thyroid hormone, steroid hormones, insulin and prolactin in rabbit fetal lung. In addition, we will try to relate the binding of corticosteroids to rabbit fetal lung nuclei and cytosol and its invervention by other hormones. Another interesting approach proposed, is the metabolism of steroids in the fetal brain of the baboon and the binding of steroids to neuroendocrine tissue of the baboon fetal brain. Other fetal tissue studies are the intestine and kidney and we will try to relate binding of steroids to the induction of enzymes with progressing gestation. We are also examining the control of steroid synthesis in the human fetal adrenal in monolayer culture.